1/* Copyright 2016 The TensorFlow Authors. All Rights Reserved.
2
3Licensed under the Apache License, Version 2.0 (the "License");
4you may not use this file except in compliance with the License.
5You may obtain a copy of the License at
6
7 http://www.apache.org/licenses/LICENSE-2.0
8
9Unless required by applicable law or agreed to in writing, software
10distributed under the License is distributed on an "AS IS" BASIS,
11WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12See the License for the specific language governing permissions and
13limitations under the License.
14==============================================================================*/
15
16#define EIGEN_USE_THREADS
17
18#include "tensorflow/core/common_runtime/constant_folding.h"
19#include "tensorflow/core/common_runtime/graph_constructor.h"
20#include "tensorflow/core/common_runtime/threadpool_device.h"
21#include "tensorflow/core/graph/node_builder.h"
22#include "tensorflow/core/graph/subgraph.h"
23#include "tensorflow/core/kernels/quantization_utils.h"
24#include "tensorflow/core/platform/init_main.h"
25#include "tensorflow/core/public/session.h"
26#include "tensorflow/tools/graph_transforms/transform_utils.h"
27
28namespace tensorflow {
29namespace graph_transforms {
30
31// Rounds any large float constants to the specified number of levels.
32Status RoundWeights(const GraphDef& input_graph_def,
33 const TransformFuncContext& context,
34 GraphDef* output_graph_def) {
35 int32_t num_steps;
36 TF_RETURN_IF_ERROR(
37 context.GetOneInt32Parameter("num_steps", 256, &num_steps));
38 TF_RETURN_IF_ERROR(ReplaceMatchingOpTypes(
39 input_graph_def, {"Const"},
40 [num_steps](const NodeMatch& match, const std::set<string>& input_nodes,
41 const std::set<string>& output_nodes,
42 std::vector<NodeDef>* new_nodes) {
43 const NodeDef& old_const_node = match.node;
44 if (!old_const_node.attr().count("dtype")) {
45 return errors::InvalidArgument("No 'dtype' attribute for Const node ",
46 old_const_node.name());
47 }
48 if (!old_const_node.attr().count("value")) {
49 return errors::InvalidArgument("No 'value' attribute for Const node ",
50 old_const_node.name());
51 }
52 const DataType old_dtype = old_const_node.attr().at("dtype").type();
53 Tensor old_tensor;
54 if (!old_tensor.FromProto(old_const_node.attr().at("value").tensor())) {
55 return errors::InvalidArgument("Decoding Tensor failed for node",
56 old_const_node.name());
57 }
58 const size_t num_elements = old_tensor.NumElements();
59 // If this isn't a float constant, or it's too small, then reuse the
60 // same node with no changes. The size is important because small
61 // constants tend to be used for more accuracy-sensitive calculations,
62 // and the benefit of shrinking them is very marginal.
63 if ((old_dtype != DT_FLOAT) || (num_elements < 16)) {
64 new_nodes->push_back(old_const_node);
65 return OkStatus();
66 }
67 const float* old_values = old_tensor.flat<float>().data();
68 float min = std::numeric_limits<float>::max();
69 float max = std::numeric_limits<float>::min();
70 for (int i = 0; i < num_elements; ++i) {
71 const float value = old_values[i];
72 min = std::min(min, value);
73 max = std::max(max, value);
74 }
75 // min_value == max_value is a tricky case. It can occur for general
76 // tensors, and of course for scalars. The quantized ops cannot deal
77 // with this case, so we set max_value to something else.
78 // It's a tricky question what is the numerically best solution to
79 // deal with this degeneracy.
80 // TODO(petewarden): Better use a tolerance than a hard comparison?
81 if (min == max) {
82 if (std::abs(min) < 0.000001f) {
83 max = min + 1.0f;
84 } else if (min > 0) {
85 max = 2.0f * min;
86 } else {
87 min = 2.0f * max;
88 }
89 }
90 Tensor rounded_tensor(DT_FLOAT, old_tensor.shape());
91 float* rounded_values = rounded_tensor.flat<float>().data();
92 const float bucket_width = (max - min) / num_steps;
93 for (int i = 0; i < num_elements; ++i) {
94 const int32_t bucket =
95 std::floor((old_values[i] - min) / bucket_width);
96 rounded_values[i] = min + (bucket_width * (bucket + 0.5f));
97 }
98
99 NodeDef rounded_const_node;
100 rounded_const_node.set_op("Const");
101 rounded_const_node.set_name(old_const_node.name());
102 SetNodeAttr("dtype", DT_FLOAT, &rounded_const_node);
103 SetNodeTensorAttr<float>("value", rounded_tensor, &rounded_const_node);
104 new_nodes->push_back(rounded_const_node);
105
106 return OkStatus();
107 },
108 {}, output_graph_def));
109
110 return OkStatus();
111}
112
113REGISTER_GRAPH_TRANSFORM("round_weights", RoundWeights);
114
115} // namespace graph_transforms
116} // namespace tensorflow
117